Bald Eagle Ddt Case Study

On By In 1

The fierce beauty and proud independence of this great bird aptly symbolizes the strength and freedom of America. But as latter-day citizens we shall fail our trust if we permit the eagle to disappear. — President John F. Kennedy

Following the enactment of the Endangered Species Act in 1973, the bald eagle was listed as "endangered" throughout the lower 48 states, with the exception of five states where it was designated as "threatened." Minnesota now has the largest numbers of nesting eagle pairs in lower 48 states. (Photo Credit: Bob Jensen)

In 1782, the bald eagle was officially declared the national symbol of the United States. It became the icon that evoked patriotism – a feeling of strength and power, of independence and courage. At the time, the population was at an estimated 100,000 birds.

In the 20th century, the population of bald eagles fell to dangerously low levels, leading to fears of extinction. Fortunately, decades of recovery efforts brought the species back from the brink – a testament to the meaningful milestones that can be achieved through effective conservation.

How we almost lost the bald eagle

A combination of wanton killing, habitat degradation and use of the pesticide DDT decimated the bald eagle population. The decline likely began as early as the late 1800s, as both eagle prey and eagles were hunted for the feather trade. By 1960, there were only 400 nesting pairs left in the lower 48.

The first eagle protections came from the Bald Eagle Protection Act of 1940, which prohibited the killing or selling of bald eagles. Despite this, populations continued to fall due to the widespread use of DDT in the 1940s and beyond – the pesticide often ending up in rivers, streams and lakes, and accumulating in fish tissue. Birds that fed on these fish laid eggs with such thin shells that they cracked during nesting.

In 1967, the bald eagle was listed as "endangered" under the predecessor to the Endangered Species Act – the Endangered Species Preservation Act of 1966. The bald eagle was one of the first species to be officially listed under the Endangered Species Act (ESA) when it was signed in 1973.

The bald eagle has never been listed as threatened or endangered in Alaska; populations there have remained stable. (Photo Credit: John Carrel)

The ESA helped save the eagle

The 1972 ban on DDT (one of EDF’s signature accomplishments) made the eagle’s recovery possible. That recovery was greatly accelerated by a combination of regulatory restrictions, nesting site protections, and reintroduction programs, which together contributed to a dramatic turnaround for bald eagle populations.

The ESA was a critical driver of all of these efforts, many of which also supported recovery of other at-risk wildlife like the peregrine falcon and brown pelican. The bedrock conservation law served to both bring public awareness to the bald eagle’s plight and to recover populations.

In 1995, the bald eagle’s status was reduced from “endangered” to “threatened,” with an estimated 4,700 nesting pairs occurring in the lower 48 states. A little over a decade later, in 2007, the species was delisted with an estimated 10,000 nesting pairs.

In 40 years, the bird saw a 25-fold increase in its population.

The ESA helped save the most iconic bird in the United States. The act provided the critical law enforcement needed in order to protect the bird across its vast range. Today, the bald eagle is once again a symbol of majestic power and unparalleled strength. We have the ESA to thank for that.

Michael Bean started working at EDF in 1977 directing wildlife conservation policy initiatives. In 2009, Michael joined the U.S. Department of the Interior as counselor to the Assistant Secretary for Fish, Wildlife and Parks, and later as the Principal Deputy Assistant Secretary. Today, Michael is back as an advisor to EDF.


Dear Congress, protect the integrity of the ESA

From 15 birds to flagship status: An American conservation movement takes flight

The “dean of endangered species protection” on the past, present and future of America’s wildlife

This entry was posted in Ecosystems, Endangered Species Act, Habitat, Partnerships and tagged bald eagle, DDT, Endangered Species Act, endangered species act success stories, endangered species list, wildlife conservation. Bookmark the permalink. Both comments and trackbacks are currently closed.

After studies showed that salmon populations were not harmed by eagle predation, this law ended a bounty system in Alaska that claimed 128,000 eagles between 1917 and 1952. The actual number of slaughtered eagles probably exceeded 150,000, since many bounties were never collected.

For a long time, the Bald Eagle Protection Act, designed also to protect the beleaguered golden eagle, was not strictly enforced. At one Wyoming ranch, for example, eagles were systematically shot for their perceived threat to livestock. According to a 1970 report, more than 770 bald eagles were shot at this ranch, and hunters were paid $25 for each carcass. Responding to a public outcry over such flagrant violations, the government began to crack down.

Just when it was finally benefiting from legal protections, the bald eagle took a heavy blow from DDT, a pesticide that enters the food chain and causes reproductive failure. Widely used after World War II to control mosquitoes and other insects, DDT was wreaking havoc among many bird species. Raptors were particularly vulnerable—over time, animals higher in the food chain accumulate more DDT.

New research on the effects of DDT challenges the long-held belief that eggshell thinning was the primary cause of reproductive failure in birds. "The thinning did occur," said Buehler, "but it was probably not actually responsible for the reproductive failure."

Rachel Carson exposed DDT poisoning in her 1962 book, Silent Spring. The pesticide was banned in the United States in 1972, but by then, over a period of about 20 years, it had done damage comparable to 175 years of persecution. The bald eagle hit a low point in 1963, when a nesting survey in the lower 48 states found only 417 pairs.

The most sweeping protections took effect in 1978, when, under the Endangered Species Act of 1973, the bald eagle was listed as endangered in 43 of the lower 48 states and as threatened in the rest. The estimated 50,000 bald eagles in Alaska are not at risk; therefore, they do not receive protection under the act.

Enforcement of the Endangered Species Act; cooperation among wildlife agencies and conservation organizations on captive-breeding programs and reintroductions; and citizen support led to a fourfold increase in lower-48 nesting populations between the mid-1970s and mid-1990s. In 1995, the U.S. Fish and Wildlife Service downgraded the bald eagle's endangered-species status in all of these states—at present, it is listed as threatened.

With the number of nesting pairs now exceeding 6,000—only Rhode Island and Vermont lack breeding populations—the Fish and Wildlife Service has announced plans to "delist" the bald eagle entirely and is working out the details of a management plan. After delisting occurs, the eagle will still be protected under the Bald and Golden Eagle Protection Act and the Migratory Bird Treaty Act. Many states have laws that continue to protect the eagle as an endangered, threatened, or "special concern" species.

A Great Conservation Story

The current bald eagle population is estimated at 100,000; more than half the birds are found in Alaska and British Columbia. Eagles will never be as abundant as they were before the arrival of Europeans. Nonetheless, their comeback is one of the great conservation stories.

Their continued success requires vigilance: Threats include oil spills—the Exxon Valdez spill in 1989 killed some 250 eagles, and the local population did not recover until 1995. Poisoning from lead fishing sinkers has also been implicated in eagle deaths. As humans encroach on eagle habitat, and vice versa, collisions with man-made structures and with vehicles are expected to rise.

Meanwhile, the National Wildlife Health Center in Madison, Wisconsin is monitoring outbreaks of avian vacuolar myelinopathy, a fatal neurological disease that first showed up in bald eagles and coots wintering at DeGray Lake in Arkansas in 1994. Twenty-nine eagles died that year; the disease has since been identified at 11 lakes in 5 states.

"We still have not been able to determine the etiology [causes] of the disease, although we suspect a chemical substance of unknown origin, most likely natural or microbial," said Tonie E. Rocke of the NWHC. "We also suspect that eagles acquire the disease secondarily through consumption of affected prey—coots and waterfowl."

As their numbers grow, bald eagles can be expected to expand their breeding range, within limits imposed by habitat destruction, human disturbance, and environmental contamination.

"Persecution from humans has declined in the last 20 years, and prime wilderness habitat has become occupied," said David Buehler, "so eagles have started moving back into human-developed areas."

Robert Winkler, a nature writer, is working on a book about his adventures with birds in the "suburban wilderness" of southern New England. Visit him at his Web site.

Recent Bird Stories by National Geographic News

Birder's Journal: It's Survey Season for Breeding Birds
Birder's Journal: Chasing Down Warblers
Africa's New Safari Trend Is for the Birds
Decline of Red-Tailed Hawks Has U.S. Scientists Puzzled
A Reason to Give Thanks: The Return of the Wild Turkey
State Bird of Hawaii Unmasked as Canadian
Harry Potter Owl Scenes Alarm Animal Advocates
Ultrarare Woodpecker Spurs Ultimate Birding Trip
"Extinct" Woodpecker Still Elusive, But Signs Are Good
Extinct Dodo Related to Pigeons, DNA Shows
Bird Extinctions May Hold Clues to Human Survival, Author Says
Tagging Hobbles Penguins, Some Researchers in Cape Town Contend
Patagonia Penguins Make a Comeback
Penguin Decline in Antarctica Linked With Climate Change
Ice Buildup Hampers Penguin Breeding in Antarctica
Evolutionary Oddities: Duck Sex Organ, Lizard Tongue
Some Ducks Let Young Be Raised by Relatives
Turkey Vultures Flourish in the U.S. Thanks to Road Kill
Forecasting the Journey South

National Geographic Bird Resources

Bald Eagles: Come Back From the Brink
Experience the Sights and Sounds of Eagles Bird-Watching Sites

North Carolina's Outer Banks
South Dakota's Black Hills
Santa Fe Area
San Francisco Area
Rocky Mountain National Park
Philadelphia Area
New York City Area
Chicago Area
Boston Area
Yellowstone National Park
Florida Keys Area

From the National Geographic Store

Guide to North American Birds
Portable Birdsong Identifier
Birder's Journal
Songbirds Puzzle


Leave a Reply

Your email address will not be published. Required fields are marked *